This invention relates to electron beam directed energy devices. In particular, this invention is directed to an electron beam device that can be used as a directed energy weapon and with modifications as a landmine detection device.
Peaking a few decades ago, there has been ongoing interest in the concept of using particle accelerators in space as weapons to destroy ballistic missile targets above the atmosphere. While much of this has been kept confidential for national security reasons, Parmentola and Tsipis presented a landmark paper on this subject in Scientific American in 1979 (J. Parmentola and K. Tsipis, “Particle-Beam Weapons,” Scientific American, 240:54-65, 1979). The authors presented scientific reasons why such weapons would be highly useful, but also dramatized the fundamental reasons why these weapons could never work.
Particle beam weapons differ from other instruments of war that carry destructive energy to the target in the form of explosive warheads in ponderous containers such as artillery shells or missile casings. Particle beam weapons, of which electron beams are just one possibility, increase the kinetic energy of a large number of individual atomic or subatomic particles and then direct them collectively against a target. Every particle in the beam that strikes the target will transfer a fraction of its kinetic energy to the target material. If enough particles hit the target in a short time, the deposited energy would be sufficient to burn a hole in the skin of the device, detonate the chemical explosives or disrupt the electronics inside including software. The most significant advantage of high-energy particle beam weapons over missiles is that, like lasers, they propagate at essentially the speed of light.
In the above article, the authors presented many small but practical problems of particle-beam weapons such as how to generate sufficient power in space, how to deal with countermeasures, and how to find targets among decoys. They also discussed two problems that they considered unsolvable. That is, the smaller problems may be considered very difficult scientific and engineering problems that may challenge practical implementation. However, even if all those could be dealt with, two significant problems remained that were unsolvable due to fundamental physical limitations that no amount of Herculean engineering could resolve.
These fundamental problems are (1) that Coulomb repulsion of a particle beam spreads the energy over a large area at reasonable distances to targets, and (2) that the near-earth magnetic field deflects the beam and is somewhat variable. (The beam is steered electrically by magnetic fields or electric fields. Mechanical steering would not be fast enough.) These two problems are shown schematically in FIG. 1.
A practical electron beam weapon would need to hit a target that is 1,000 km away with a 1000 amp beam having an energy of 1 GeV for 0.1 msec. Furthermore, the beam needs to be 1 cm or so in diameter at the target in order for the deposited energy to be sufficiently intense. The authors indicate that a 1 GeV electron beam of 1000 amps would spread from an initial 1 cm diameter to a 5 meter diameter at 1,000 km due to Coulomb repulsion. They also indicate that a 1 GeV beam would be deflected by 1,000 km over a distance of 1,000 km due to the earth's magnetic field. It is well known that the earth's magnetic field is also not completely steady. Under such unstable conditions, it would be close to impossible to make a workable weapon that could reliably hit a target 1000 km away with enough energy to destroy it. Also, there are only 400 or so seconds to distinguish between multiple targets and decoys in the initial phase of a ballistic missile's trajectory and then destroy the targets. There is more time, however, near the apogee section of travel in which to detect and destroy the missile compared to its ascent and reentry phases.
Much has been learned about near-earth magnetic fields in recent years. The near-earth magnetic field is 97% due to the earth's core, and ranges in magnitude from 30,000 nanoTesla (nT) at the equator to 50,000 nT at the poles. The solar quiet magnetic field variation is a manifestation of an ionospheric current system. Heating at the day side and cooling at the night side of the atmosphere generates tidal winds, which drive ionospheric plasma against the geomagnetic field inducing electric fields and currents in the dynamo region between 80-200 km in height. The current system remains relatively fixed to the earth-sun line and produces regular daily variations that are directly seen in the magnetograms of geomagnetic “quiet” days. On “disturbed” days there is an additional variation that includes superimposed magnetic storms. Because the geomagnetic field is strictly horizontal at the magnetic equator, there is an enhancement of the effective Hall conductivity, called the Cowling conductivity, which results in an enhanced eastward current, called the equatorial electrojet, flowing along the day side magnetic equator. In addition, auroral electrojets flow in the auroral belt and vary in amplitude with different levels of magnetic activity.
The solar quiet fields are on the order of 10-50 nT, depending upon component, latitude, season, solar activity, and time of day. The magnetic signature of the equatorial electrojet can be about 5-10 times that of solar quiet, and that of the auroral electrojets can vary widely from 10-20 nT during quiet periods to several thousand nT during major magnetic storms. It is complex, but the near-earth magnetic field has both a significant predictable varying component and also a significant non-predictable varying component.
The prior art lacks a workable concept of how to use an electron beam directed energy device that can overcome Coulomb repulsion and the earth's varying magnetic field and steer the beam such that it can impact and destroy objects approximately 1000 km distant, such as missiles in outer space.
Another major unsolved problem is the detection and/or the destruction of landmines. Since their early widespread use in the First World War, landmines have proved to be an inexpensive and effective military weapon. With landmines, an enemy is denied safe access to specific areas. They can delay, divert or destroy enemy forces—including those numerically and technologically superior. They can impede supply lines and demoralize a foe. Antitank landmines can interfere with vehicular flow and antipersonnel landmines protect antitank landmines, defend large and small areas and effectively deny access to bridges, borders and other areas of important pedestrian flow in specific regions. This will disrupt commerce, instill fear among non-combatants, and act as a psychological weapon to undermine confidence in governments. They are also effectively used in booby-traps. Costing as little as $3 to $30 each, these are perhaps the most cost-effective weapons available in any military arsenal—thus assuring their ubiquity.
There are estimated to be 50 to 100 million landmines including new placements and those left over (but still operational) from forgotten old conflicts. These latter are particularly injurious to civilians including farmers and young persons playing in fields. It is a worldwide-recognized hazard. In a concerted effort to remove this scourge, 123 countries met in 1997 to sign the “Convention on the Use, Stockpiling, Production and Transfer of Anti-Personnel Mines and on Their Destruction.” There are many countries that have not as yet signed this agreement. However, all would agree that leftover landmines are a major health and societal problem in many areas of the world. Finding and removing both simple and sophisticated concealed explosives in asymmetrical warfare and terrorism is an equally important need.
From a technical viewpoint, finding buried landmines and concealed explosives is difficult since there is usually only access to one side of the object. With this limitation, methods that have been proposed include penetrating radiation (neutron and photon) plus acoustic energy. For example, U.S. Pat. No. 6,473,025 was issued to G. Stolarczyk for a ground penetrating radar for landmine detection. Detection of anomalous objects in this patent, however, takes the form of measuring secondary emissions (activation) or radiation scattering. This is far less efficient than detection in a direct transmission or shadow image mode in which case there are many more measurable events per incident photon. As an analogy, cancers deep within otherwise normal organs are commonly identified with x-ray imaging, but only because the source of x-rays is on one side of the subject and a detector is on the other side. This is called back-illumination and it produces a shadow image of the subject at the detector with observable local variations in x-ray attenuation. If there were only access to one side of a human subject, x-radiation would be practically worthless in finding occult cancer.
X-rays are produced when energetic (in comparison to rest-mass energy) electrons are slowed, change direction, or stopped suddenly when they impact an atom of relatively high atomic number. This is called bremsstrahlung or breaking radiation. Electrons can travel in the atmosphere and to a lesser extent in soil. As the beam electrons interact with high Z atoms, they undergo directional changes before they stop. The resulting x-radiation is emitted in all directions from a plume within the material. X-rays are also emitted when impacted atoms undergo induced orbital transitions if energetically possible. These are also emitted in all directions.
The prior art lacks a method using an electron beam device to produce a sub-earth surface source of x-radiation. The prior art also lacks an electron beam device to locate or destroy buried objects including explosives.